1. Field of the Invention
The present invention relates to a video game and, more particularly, the technology for shading an object in a virtual space.
2. Related Background Art
In recent years a variety of rendering techniques have been studied for shading in the surface of the object placed in a virtual, three-dimensional space in the field of video games. For shading the object placed in the virtual 3D space, luminance computation is executed in consideration of various factors including the property of a light source, the positional relation among the light source, the object, and the view point, the texture of the surface of the object, and so on. Then realistic shading can be made for the image by drawing the image after transparent transformation, based on the result of the luminance computation.
However, the phenomena described below can be encountered when the projection image is drawn so as to accurately reflect the result of the luminance computation. For example, where the object such as a character or the like is placed in the virtual space under presence of little light, the whole projection image becomes so dark that the character is imperceptibly fused into the background. On the other hand, where the object is placed in the very bright virtual space, the whole projection image becomes so bright that the character is imperceptibly fused into the background. When the projection image is drawn so as to accurately reflect the result of the luminance computation in this way, there occurs some cases wherein the object becomes hard to recognize in the projection image drawn. It is thus desirable that at least an object to be noted be definitely discriminated from the background image so as to be recognized by the user.